Field of the Invention
The invention relates to a configuration for processing wafers having fabrication units, measuring units, and a transport system for conveying a cassette of the wafers between the fabrication units and the measuring units.
These types of devices contain a number of fabrication units, with which various finishing steps are carried out. These finishing steps include various treatment steps in etching processes, wet chemical processes, diffusion processes, and various cleaning techniques such as CMP (Chemical Mechanical Polishing). One or more fabrication units are provided for each of these finishing steps. In addition, measuring units are provided, in which the quality of the wafer processing can be checked.
The overall fabrication process is subject to stringent purity requirements, for which reason the fabrication units and measuring units are disposed in a clean room or a system of clean rooms.
The wafers are supplied to the individual fabrication units in cassettes in predetermined batch sizes by way of a transport system. The wafers are also removed in cassettes by way of the transport system, after being processed in the fabrication and measuring units.
The transport system typically includes a conveyor system, which is constructed in the form of roll conveyors, for instance. A predetermined number of cassettes are supplied to a fabrication unit or measuring unit for processing via the transport system. The fabrication unit or measuring unit respectively includes a loading and unloading station, via which a respective cassette with wafers can be inserted. After all of the wafers of a cassette have been processed in the fabrication unit or measuring unit, the cassette with the wafers is output again by way of the loading and unloading station and is transported out via the conveyor system.
Because of the relatively long transport paths between the individual fabrication and measuring units and the different processing capacities of the fabrication and measuring units, storage systems, such as stockers, are provided in near the fabrication and measuring units, and these stockers are a component of the transport system. Cassettes with wafers can be stored in a stocker under clean-room conditions and can be fed to the individual fabrication and measuring units as needed.
One disadvantage of this method is the large installation expenditure for the transport system. Specifically, storing the cassettes in the stockers is time-consuming and costly. Another disadvantage is that the conveyor system consists of linear systems such as roll conveyors, which can only be branched to a limited degree. The general result of this is that the construction of the transport system substantially determines the configuration of the fabrication units and measuring units. Therefore, the fabrication units and measuring units are usually not arranged in accordance with their functionalities. This leads to a certain inefficiency in the transport of individual wafers.
A further disadvantage is the need to wait for all of the wafers of a cassette to be processed in a fabrication or measuring unit before the entire batch in the cassette is forwarded to the transport system via the loading and unloading station in order to be transported out. If, for example, the wafers of a cassette are first processed in a fabrication unit, and then the processing quality is checked in a measuring unit, then all of the wafers of a cassette must be processed before the checking process can occur in the measuring unit. Only then can subsequent additional measures be taken in dependence upon the measurement results. The throughput times of the cassettes with the wafers through the system are therefore undesirably high.
U.S. Pat. No. 5,803,932 describes a processing system for processing wafers. This processing system includes a loading/unloading section, a processing section and an interface section. In addition, a transport mechanism and at least two waiting sections are provided.
The transport mechanism is located between the loading/unloading section and the interface section. A plurality of processing units, which form the processing section, are disposed on either side of the transport mechanism. The wafers are transported on the transport mechanism either in the direction of the loading/unloading section or in the direction of the interface section.
U.S. Pat. No. 5,443,346 describes a transport system for transporting wafers in a clean room. The wafers are first transported in first cassettes by way of an interbay conveyor system, arriving at interface equipment. In the interface equipment, the wafers are removed from the first cassettes and reloaded into second cassettes in a predetermined arrangement. Then, the second cassettes are successively fed to different processing units by way of an intrabay conveyor system, where the wafers are processed in a variety of ways.
Published German Patent Application DE 195 14 037 A1 relates to a transport device for transporting substrates. The transport device is constructed as a turntable, which is driven at a constant cycle frequency. The substrate can be fed to a processing station, which is provided outside the turntable by means of a rotating substrate gripper.
Published Japanese Patent Application JP 08268512 A relates to a storage unit for storing substrates. The storage unit includes a sorting unit, by means of which the substrates are automatically sorted and moved into or out of the storage unit in cassettes.
It is accordingly an object of the invention to provide a configuration for processing wafers which overcomes the above-mentioned disadvantages of the prior art apparatus of this general type. In particular, it is an object of the invention to optimally minimize the throughput time for processing a wafer in configuration of the above described type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a configuration for processing wafers that includes: a plurality of fabrication units for carrying out individual fabrication steps; a plurality of measuring units for checking the fabrication steps; a transport system for transporting cassettes having a predetermined batch size of wafers, the transport system connecting the plurality of the fabrication units and the plurality of the measuring units; and a fabrication cell including a combination of functionally allocated units selected from the group consisting of the plurality of the fabrication units and the plurality of the measuring units. The fabrication cell includes a loading and unloading station for receiving the cassettes with the wafers and for outputting the cassettes with the wafers. Individual wafers are supplied in a parallel manner to the functionally allocated units in the fabrication cell. The plurality of the fabrication units, the plurality of the measuring units, the transport system, and the fabrication cell are located in at least one clean room.
In accordance with an added feature of the invention, one or more fabrication cells are provided, in which several fabrication and/or measuring units are combined. Each fabrication cell includes a loading and unloading station for delivering cassettes, with wafers, in and out. Within the fabrication cells, the wafers can be individually supplied to the fabrication units and/or measuring units in a parallel fashion.
The fabrication units and measuring units are allocated according to function, whereby the functions of the individual fabrication and measuring units expediently make up a fabrication process.
The essential advantage of such a fabrication cell is that the wafers of a cassette no longer need to be serially processed in the individual fabrication units and measuring units. Rather, the wafers can be individually fed to the fabrication and measuring units as needed, making it possible to process the wafers within a fabrication cell in a parallel fashion. What is particularly advantageous is the ability to feed a wafer to the allocated measuring unit immediately after it is processed, so that the processing quality can be checked. The fabrication cell advantageously may additionally include a suitable fabrication unit in which the wafer can be post-processed immediately after the check in the measuring unit.
The parallelism of the wafer finishing steps in the fabrication cell prevents unnecessary wait times at the individual fabrication and measuring units, so that a low throughput time of the wafers through the fabrication cell can be achieved.
A further advantage is that the individual wafers are suppliable to the fabrication and measuring units within a fabrication cell without intermediate storage. On one hand, this further reduces the throughput times of the wafers through the configuration. On the other hand, substantial cost savings are achieved by forgoing storage systems.
The construction of the overall configuration is substantially simplified by combining fabrication and/or measuring units into fabrication cells. In particular, the transport system for transporting cassettes with wafers between the individual fabrication cells can have a simple construction.
In accordance with an additional feature of the invention, a sub-transport system transports individual wafers between the functionally allocated units (fabrication and/or measuring units) in the fabrication cell.
In accordance with another feature of the invention, handling devices are provided at the conveyor system, for feeding individual ones of the wafers to the functionally allocated units (fabrication and/or measuring units) of a fabrication cell and for removing the individual wafers from the functionally allocated units of the fabrication cell.
In accordance with a further feature of the invention, there is provided a first fabrication cell including a first sub-transport system, and a second fabrication cell linked to the first fabrication cell. The second fabrication cell includes a second sub-transport system. A handover station connects the first sub-transport system and the second sub-transport system to link together the first fabrication cell and the second fabrication cell.
In accordance with a further additional feature of the invention, the first fabrication cell includes a loading station for receiving the cassettes with the wafers; and the second fabrication cell includes an unloading station for outputting the cassettes with the wafers.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in apparatus for fabricating wafers, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.